/*
 * jQuery One Page Nav Plugin
 * http://github.com/davist11/jQuery-One-Page-Nav
 *
 * Copyright (c) 2010 Trevor Davis (http://trevordavis.net)
 * Dual licensed under the MIT and GPL licenses.
 * Uses the same license as jQuery, see:
 * http://jquery.org/license
 *
 * @version 3.0.0
 *
 * Example usage:
 * $('#nav').onePageNav({
 *   currentClass: 'current',
 *   changeHash: false,
 *   scrollSpeed: 750
 * });
 */
layui.use('jquery', function () {
    var jQuery = layui.$;

    ; (function ($, window, document, undefined) {

        // our plugin constructor
        var OnePageNav = function (elem, options) {
            this.elem = elem;
            this.$elem = $(elem);
            this.options = options;
            this.metadata = this.$elem.data('plugin-options');
            this.$win = $(window);
            this.sections = {};
            this.didScroll = false;
            this.$doc = $(document);
            this.docHeight = this.$doc.height();
        };

        // the plugin prototype
        OnePageNav.prototype = {
            defaults: {
                navItems: 'a',
                currentClass: 'current',
                changeHash: false,
                easing: 'swing',
                filter: '',
                scrollSpeed: 750,
                scrollThreshold: 0.5,
                begin: false,
                end: false,
                scrollChange: false
            },

            init: function () {
                // Introduce defaults that can be extended either
                // globally or using an object literal.
                this.config = $.extend({}, this.defaults, this.options, this.metadata);

                this.$nav = this.$elem.find(this.config.navItems);

                //Filter any links out of the nav
                if (this.config.filter !== '') {
                    this.$nav = this.$nav.filter(this.config.filter);
                }

                //Handle clicks on the nav
                this.$nav.on('click.onePageNav', $.proxy(this.handleClick, this));

                //Get the section positions
                this.getPositions();

                //Handle scroll changes
                this.bindInterval();

                //Update the positions on resize too
                this.$win.on('resize.onePageNav', $.proxy(this.getPositions, this));

                return this;
            },

            adjustNav: function (self, $parent) {
                self.$elem.find('.' + self.config.currentClass).removeClass(self.config.currentClass);
                $parent.addClass(self.config.currentClass);
            },

            bindInterval: function () {
                var self = this;
                var docHeight;

                self.$win.on('scroll.onePageNav', function () {
                    self.didScroll = true;
                });

                self.t = setInterval(function () {
                    docHeight = self.$doc.height();

                    //If it was scrolled
                    if (self.didScroll) {
                        self.didScroll = false;
                        self.scrollChange();
                    }

                    //If the document height changes
                    if (docHeight !== self.docHeight) {
                        self.docHeight = docHeight;
                        self.getPositions();
                    }
                }, 250);
            },

            getHash: function ($link) {
                return $link.attr('href').split('#')[1];
            },

            getPositions: function () {
                var self = this;
                var linkHref;
                var topPos;
                var $target;

                self.$nav.each(function () {
                    linkHref = self.getHash($(this));
                    $target = $('#' + linkHref);

                    if ($target.length) {
                        topPos = $target.offset().top;
                        self.sections[linkHref] = Math.round(topPos);
                    }
                });
            },

            getSection: function (windowPos) {
                var returnValue = null;
                var windowHeight = Math.round(this.$win.height() * this.config.scrollThreshold);

                for (var section in this.sections) {
                    if ((this.sections[section] - windowHeight) < windowPos) {
                        returnValue = section;
                    }
                }

                return returnValue;
            },

            handleClick: function (e) {
                var self = this;
                var $link = $(e.currentTarget);
                var $parent = $link.parent();
                var newLoc = '#' + self.getHash($link);

                if (!$parent.hasClass(self.config.currentClass)) {
                    //Start callback
                    if (self.config.begin) {
                        self.config.begin();
                    }

                    //Change the highlighted nav item
                    self.adjustNav(self, $parent);

                    //Removing the auto-adjust on scroll
                    self.unbindInterval();

                    //Scroll to the correct position
                    self.scrollTo(newLoc, function () {
                        //Do we need to change the hash?
                        if (self.config.changeHash) {
                            window.location.hash = newLoc;
                        }

                        //Add the auto-adjust on scroll back in
                        self.bindInterval();

                        //End callback
                        if (self.config.end) {
                            self.config.end();
                        }
                    });
                }

                e.preventDefault();
            },

            scrollChange: function () {
                var windowTop = this.$win.scrollTop();
                var position = this.getSection(windowTop);
                var $parent;

                //If the position is set
                if (position !== null) {
                    $parent = this.$elem.find('a[href$="#' + position + '"]').parent();

                    //If it's not already the current section
                    if (!$parent.hasClass(this.config.currentClass)) {
                        //Change the highlighted nav item
                        this.adjustNav(this, $parent);

                        //If there is a scrollChange callback
                        if (this.config.scrollChange) {
                            this.config.scrollChange($parent);
                        }
                    }
                }
            },

            scrollTo: function (target, callback) {
                var offset = $(target).offset().top;

                $('html, body').animate({
                    scrollTop: offset
                }, this.config.scrollSpeed, this.config.easing, callback);
            },

            unbindInterval: function () {
                clearInterval(this.t);
                this.$win.unbind('scroll.onePageNav');
            }
        };

        OnePageNav.defaults = OnePageNav.prototype.defaults;

        $.fn.onePageNav = function (options) {
            return this.each(function () {
                new OnePageNav(this, options).init();
            });
        };

    })(jQuery, window, document);

});